98 Cobra Alarm
 

First let me say I'm new to this, so I hope I'm doing this correctly. I just got a 98 Cobra convertible. I have a strange problem. When you lock the car with the remote and a loud truck rolls by it seats off the alarm. It also turns on the check engine light. We have the software to read and reset the computer. The trouble log says it was an alarm fault. I have reset it twice. I talked to a Ford dealer, thinking a motion sensor went bad and he cleaims there are no motion sensors in the car but that an after market one may have been added. ANY IDEALS??

Thanks
Harry